The present invention relates to a liquid delivery apparatus and liquid delivery method. Particularly, the present invention relates to the liquid delivery apparatus and liquid delivery method for delivering liquid by controlling the flow of a minute amount of liquid in a minute or micro liquid passage.
Recently, a variety of health diagnostic chips have been developed. Almost all these health diagnostic chips are card-type devices having a micro liquid passage structure called a MICROTAS (μ-TAS: Micro Total Analysis System). The micro or fined liquid passage is very useful because microscopic amounts of sample need to be extracted from a biologic body. Further, the entire apparatus including the health diagnostic chip miniaturized by employing the micro liquid passages can be can be used not only in relatively large hospitals, but also for POCT (Point Of Care Test: field diagnostics thereof) applications in clinics and at home.
In macro systems, a pump is generally used as liquid delivery means. However, in micro liquid passages for manipulating extremely small quantities of fluids, a dead volume generated in a tube connected to the pump is not ignorable.
Methods advantageously used for liquid delivery in POCT applications include using a centrifugal force as a drive source. The advantage of this liquid delivery method is that no dead volume is generated and that a large number of processes can be executed concurrently and simultaneously. For example, Japanese Patent Application Laid-Open Publication No. 2001-503854 discloses a micro liquid delivery method adapting a capillary valve system. In this micro liquid delivery method, a flow of fluid is blocked by a capillary force generated in a micro liquid passage. Then, the centrifugal force generated by rotation of a rotary substrate breaks equilibrium of force so as to achieve liquid delivery from one micro chamber to other micro chamber.
However, according to the micro liquid delivery method disclosed in Japanese Patent Application Laid-Open Publication No. 2001-503854, because the centrifugal force generated by rotation serves as a drive source, an arrangement position of the valve is limited to the radially outward direction (centrifugal direction) of a rotary shaft of the rotary substrate wit respect to the supply side micro chamber. Further, the liquid delivery is also essentially limited only to one direction, namely, the centrifugal direction. Due to such restrictions relating the drive principle, the micro liquid delivery method disclosed in Japanese Patent Application Laid-Open Publication No. 2001-503854 restricts the design flexibility of the rotary substrate, places limitations upon the arrangement of liquid passage structure and behaviors of delivered liquid, and can not achieve liquid delivery with multiple functions.